Carburetor having a vacuum regulated metering rod



March 7, 1967 J. BE'RZLAPA 3,307,839

CARBURETOR HAVING A VACUUM REGULATED METERING ROD Filed Dec. 1, 1965 2Sheets-Sheet 1 l2 7 HE A ,5

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ATTORNEY United States Patent 3,307,839 CARBURETOR HAVING A VAQUUMREGULATED METERHNG ROD Juris Berzlapa, St. Louis, Mo., assignor to ACEIndustries, Incorporated, New York, N.Y., a corporation of New JerseyFiled Dec. 1, 1965, Ser. No. 510,811 6 Claims. (Cl. 261--60) Thisinvention relates to a carburetor. It relates in particular to acarburetor utilizing a controlled metering rod for more accuratelyregulating flow of fuel to the carburetor mixing conduit.

In carburetors of the type contemplated, the flow of fuel passing fromthe carburetor fuel bowl to the mixing conduit is regulated to someextent by a metering rod positioned in an orifice connecting the sourceof fuel with the mixing conduit. The primary function served by ametering rod is to afford the carburetor a higher degree of efliciencyand full economy. Ideally, the metering rod for-med end is -so contouredto provide an optimum flow of fuel to themixture conduit under allengine opertaing conditions. This, however, is not always possible.Particularly at low and idle speeds, regulation of the metering rod toobtain a proper air fuel mixture becomes difficult. For example, thedegree of vacuum at the engine intake manifold will vary within therange of about 25 inches of mercury to about a few inches of water.Engine loading and speed will of course be reflected in the vacuumcondition at the intake manifold. Thus, with respect to the operation ofan ordinary metering rod responsive to engine vacuum, the rod will beadjusted an amount directly proportional to the degree of engine vacuum.

Fuel control is achieved by regulating the position of the metering rodin an orifice to alter the flow of fuel passing into the carburetordischarge nozzle as the demand for fuel is varied by the engine. Onesuch regulating means successfully utilized, includes a pneumatic or airmotor arrangement connected to a source of vacuum such as the engineintake manifold, whereby variations in manifold vacuum are reflected ina comparable adjustment in the metering rod position.

It has been found that while the fuel metering rod above described isbeneficial in many respects to carburetor operation, under somecircumstances it is desirable that closer fuel control be exercised toimprove engine combustion. Further, where an air motor actuator isutilized, an inadequate reaction rate is present between the need for aricher air-fuel mixture, and the delivery of sufficient fuel to providesuch a mixture is often excessive. This follows since the normal airmotor and metering rod arrangement is designed to respondproportionately to the degree of manifold vacuum and consequently, inthe usual instance of engine operation, intake manifold vacuum variesdirectly with engine speed and load. Thus, when a sudden demand forgreater engine power occurs, the proper amount of fuel to mix withincoming air is unavailable.

Also, it has been found that under certain engine speeds and loads,excessive fuel delivery to the discharge nozzle results in an over-richair fuel mixture and the creation of undesirable amounts of unburnedhydrocarbons which discharge to the atmosphere with engine exhaustfumes. Engine operation under such circumstances is not onlyuneconomical, it tends to aggravate the frequent problem of airpollution due to the emission of unburned hydrocarbons andotherundesirable matter into the atmosphere.

It is therefore an object of the invention to provide an improvedcarburetor including a fuel metering device to accurately andeconomically furnish a proper air fuel mixture to the engine under allopertaing conditions. A further object is to provide a carburetor of thetype described including a fuel system adapted to assure optimum airfuel mixtures at load speeds as well as at idle speed. A still furtherobject is to provide a fuel metering system for a carburetor includingan automatically adjustable metering rod. Still another object is toprovide an air motor regulated fuel metering rod so arranged toinstantaneously respond to engine conditions, said motion giving astepped-up performance particularly at low engine speeds.

The foregoing objects, together with others not specifically enumeratedwill be clear to those skilled in the art from the followingdescription.

The invention as herein disclosed is directed to a wellknown carburetorconstruction utilizing a fuel metering rod cooperative with an orificeor jet formed in the base of the carburetor fuel well, the latter whichforms a portion of the carburetor body. The well portion of the body isdisposed within the carburetor fuel bowl. The metering rod is arrangedsuch that the tapered or metering end is operatively positioned withinthe fuel metering jet to define a variable annulus.

The upper end of the metering rod is retained in an air motor assemblyresponsive to manifold vacuum.

Thus, the metering rod is connected to a displaceable diaphragm in theair motor which adjusts automatically in response to variations inengine manifold, which normally reflects engine speed and load. However,to avoid the normal reaction of the air motor to over-adjustment at lowengine speeds, which would provide an over-rich air fuel mixture, and toassure an adequately rich fuel mixture as needed, means is prvoided forminimizing or overcoming the effects of intake manifold vacuum on theair motor by at least partially spoiling the vacuum as the throttle isadvanced from engine idle position.

The invention is presently illustrated and described as incorporatedinto the body of a single barrel carburetor similar to the model shownin U.S.P. 3,189,331. It is understood however, that the followingdescription of the fuel metering device is for the purpose ofillustrating a particular structure which may be applied equally as wellto other forms of carburetors such as multi-barrel units and the like.

Referring to FIGURES 1 and 2, the carburetor con-. sists essentially ofa casting 10, which is formed with a fuel and air mixture conduit 12,and a fuel bowl cover portion 14 from which depends an accelerating pumpcylinder 16, an accelerating fuel passage 18, and a fuel well structure20. Mixture conduit 12 is connected by a flange 13 to intake manifold Mof an internal combustion engine E. In the lower part of the conduit 12there is rotatably mounted a throttle valve 22 fixed to a throttle shaft24 journalled in appropriately aligned apertures in body casting It). Inthe upper portion of the fuel air mixture conduit 12 there is similarlymounted for rotational movement an unbalanced choke valve 26 fixed to achoke valve shaft 28, which is also journalled in aligned aperturesthrough the body casting 10.

The top of mixture conduit 12 is connected to an air filter 29,partially shown in cross-section in FIGURE 2. Between the upper andlower portions of mixture conduit 12 is formed a venturi or air flowrestricting surface portion 30. A small booster venturi 32 is formedintegrally with body casting 10 and has an inner venturi surface 34coaxially aligned with the mixture conduit 12 and the primary venturisurface 30.

A fuel bowl 36 is fixed beneath fuel bowl cover 14 and is held with itsrim against a gasket 38 fitted between the rim of the fuel bowl 36 andmatching portions of the fuel bowl cover 14. A float structure 40 ispivotally mounted from pin 42 journalled in a depending portion of fuelbowl cover 14. A lever arm of float lever 43 fixed to float 4t abuts thelower end of a needle valve 44 having an upper tapered end extendinginto a valve seat 46 of the inlet 47 to the fuel bowl 36.

Fuel is forced under pressure by pump 59 from the fuel tank 15 throughfuel line 19 and to carburetor inlet 47. When fuel level in bowl 36 islow, float 40 drops commensurably and lever arm 43 permits valve 44 tobe displaced to an open position under fuel pressure. Fuel then flowsinto bowl 36 until reaching a predetermined level. Needle valve 44 isclosed by the upward urging of float lever 43 as the fuel level rises.

Referring to FIGURES 3, 4, and 5, the lower end of fuel well 20 isclosed by a threaded fitting 56 having a central orifice 69 which isformed to provide the metering jet for the flow of fuel from fuel bowl36 to mixture conduit 12. A screw driver slot 57 is provided in thelower side of fitting 56 to permit removal. The upper end of fuel well20 intersects fuel passage 58 directed downwardly into secondary venturi32. A nozzle fitting 60 is held in the end of passage 58, one end of thefitting 60 extending into the secondary venturi 52. A fuel emission tube62 is fitted and supported within well 2%.

Metering rod 66 is suspended within fuel well 20, having a metering end68 formed with varying diameters. The formed end 68 is positioned withinthe main fuel jet orifice 69 for operation in response to enginerequirements. Flow of fuel through main orifice 69 is controlled bymetering rod 66 and in accordance with that portion of the formed end 68which is positioned within opening 69.

Metering rod 66 is accurately contoured at lower end 68 in fuel orifice69 to permit maximum fuel eflicienoy. In particular, with the enginerunning at idle, the lower cylindrical end 55 of metering rod 66 fitsclosely with adjoining walls of orifice 69, thereby defining a minimumannulus to form a suficiently large fuel passage to sustain the engineat idle. This arrangement permits satisfactory and economical engineoperation without overenrichment of the fuel mixture, a condition thatpromotes improved utilization of fuel energy.

Referring to FIGURES 3, 4, and fuel well 26 includes a relatively narrowelongated channel formed substantially uprightly in the carburetor walland opening at the upper end into an enlarged bore 48 along an outwardly tapered surface 49. Peripheral shoulder 51 formed on taperedsurface 49 provides a rigid annular seat for flexible diaphragm 52 whichis displaceable to inner and outer positions.

The air motor for actuating metering rod 66 includes basically a sealedplenum chamber 95 formed in bore 48 and having an inlet communicatingsaid chamber to the engine intake manifold M. As shown in FIGURE 3,plenum-bhamber 9-5 is formed in fuel bowl cover 14 including a passage71 which in turn is connected to passage 72 in the wall of casting l0.Passage 72 extends downwardly terminating at the lower face of casting10, and is provided with a constricted portion 73 which may be a smallbore insert, press fitted into passage 72. The size of passage 73 isdetermined or calibrated in accordance with a specific carburetor andmotor characteristic. The function of passage 73 is to regulate air flowbetween intake manifold M and passage 72. However, the open area of saidpassage 73 is also determined by, and is coordinated with the size ofpassage 74 as will be hereinafter noted.

A second passage means 74 likewise formed in a Wall of casting defines acalibrated limited flow duct which may include an orifice, or merely beconstricted in its entirety to meter air flow therethrough. Secondpassage means 74 terminates at a port 76 opening into mixture conduit12. Port 76 is so positioned in a wall of mixture conduit 12, and withrespect to throttle valve 22, as to be either substantially blocked whenthe throttle is in idle position or to be slightly downstream of thethrottle plate edge. However, preferably the lower peripheral edge ofplate 22 is contiguous with the upper edge of port 76. Operationally,when the throttle plate is adjusted slightly from idle position as shownin FIGURE port 76 will be disposed on the throttleupstr'earn side andconsequently exposed to substantially atmospheric pressure. Otherwise,at throttle idle, passages 73 and 76 are simu1- taneously exposed tointake manifold vacuum.

Referring to FIGURES 4 arid the structure of the air motor comprisesessentially diaphragm 52 having a peripheral edge urged into sealingcontact with shoulder 51. Diaphragm 52 is centrally positioned on hub 59and held in abutment with shoulder 54 by asap-like member 78, beingdownwardly biased by spring 77.

A spring retainer 79 includes a peripheral lip 81 urged into contactwith diaphragm 52, said. retainer being com pressibly held by a sealingcover member 82;L;a;:ing a flange 33 frictionally retained in theopening of bore 48 by a washer 87. One or more openings 86 are formed inthe wall of spring retainer 79. A depression at the center of cover 82provides an abutment for the upper end of metering rod head 53 therebylimiting upward movement of the rod to locate tapered end 55 in idleposition within orifice 69.

Operation of the above-described device is best understood withreference to FIGURES 6 and 7 and the graph of FIGURE 8. With the engineoperating at idle speed, throttle plate 22 will be positioned as shownin FIGURE 6 with the peripheral edge in engagement with, or contiguouswith the adjacent wall of mixing conduit 12. Said throttle edge as shownparticularly in FIGURE 6 is disposed immediately above port 76, oralternatively in such position as to define a closure to port 76 therebyimpeding or preferably precluding flow of air through said port. Thus,with the engine idling, a manifold depression of approximately 19 inchesof mercury will be established in the intake manifold and communicatedthrough constricted passage 72, passage 71 and openings 86 to plenum inbore 43. The vacuum in said plenum is sufficient to overcome thedownward biasing action of spring 77 thus withdrawing diaphragm 52 toits maximum upward position. Cylindrical end 55 is therefore disposedwithin orifice 69 to provide an optimum opening for fuel flow to thenozzle 60. As previously noted, this fuel flow is calibrated to mostefiiciently maintain the engine at idle speed by virtue of theaccurately formed annulus between rod end 55 and the adjacent walls oforifice 69.

Thus, at engine idle, diaphragm 52 will remain as shown in FIGURE 4,completely withdrawn to its upper maximum. Head 53 is thus disposed inabutment with depression 68 thereby maintaining the location ofcylindrical portion 55, in orifice 69. This is illustrated by line A-Bin the graph of FIGURE 8.

Normally, in an air motor controlled metering rod not embodying theinvention, as the throttle plate is displaced from idle position toprovide additional power to the engine, the intake manifold depressionwill be depressed. The effect communicated to the plenum chamber is thatthe withdrawing force on diaphragm 52 is lessened and consequently thediaphragm will be displaced slightly downward by the biasing of spring77 to move the metering rod further into the orifice 69 therebyproviding a greater annulus for fuel flow. In this type arrangement,however, the additional fuel afforded is insufiicient to properlymaintain engine speed.

In accordance with the disclosed arrangement and again referring toFIGURE 7, as throttle plate 22 is displaced downwardly from idleposition to provide a greater flow passage in mixture conduit 12, theperiphery of plate 22 Will sweep past port76 thereby disposing thelatter upstream of the throttle plate. Passage 72 is now communicatedinstantaneously by way of passage 74 with atmosphere thereby in effectcollapsing or reducing the or slightly richer air fuel mixture.

Again regarding operation of the carburetor, referring to FIGURE 8,instantaneous depression or falling of the air motor vacuum isillustrated by the family of curves B-C, B-Cl, B-CZ, and BC3. The abruptstep down in the curve from a substantially constant slope as at AB, toa curve characterized by a sharp break in air motor vacuum at a pointjust past engine curb idle. This is represented by a substantiallyvertical segment of the curve terminating at C.

Thereafter, for further decerases in intake manifold vacuum, thecomparable decrease in air motor vacuum will be relatively minorexemplary of which is by curve C, and D having a substantial portionthereof representing a constant air motor vacuum for a period of intakemanifold vacuum decrease.

While the graphical representation of FIGURE 8 depicts a number ofcurves adapted to different carburetors, the common characteristic ofeach curve is the abrupt step down defined between points B, C, and D ascontrasted with the relatively constant slope typical of the vacuumrelationship between the air motor and the intake manifold, where thepresent invention is not utilized.

It is clear from the foregoing that the carburetor presently describedaffords several advantages heretofore unrealized in the art. For onething, a more accurate and closely controlled metering of fuel to thedischarge nozzle assures a more economical utilization of the fuelenergy at all engine speeds. Further, and by no means secondly inimportance, is the minimization or complete elimination of undesirablehydrocarbon emissions which would tend to aggravate a smog problem.Also, the novel arrangement permits automatic adjustment of thecarburetor air fuel mixture calibration in immediate response to aparticular demand or requirement such as a minor load imposed on theengine in response to a variation in intake manifold vacuum.

The structure asherein described may be varied slightly by the additionof springs and the like to supplement the action of the air motor.However, successful operation of the carburetor in the mannercontemplated will depend primarily on the relative size of therespective passages 73 and 74 which are designed to impede air flow bothto and from the air motor thereby controlling fuel feed to the engine.

It is appreciated by those skilled in the art that the foregoinginvention embodies an improvement in carburetors not heretofore known orpractical. More specifically, the desirable features of an air motorcontrolled metering rod are utilized to the fullest. However, underpredetermined conditions, the function of the air motor is in effectby-passed by the spoiling of air motor vacuum in order that the-meteringrod might be utilized more advantageously.

journalled in the mixture conduit and being operable to regulate thepassage of air and fuel mixture therethrough, a fuel bowl formed in saidbody holding a supply of fuel, a venturi in said body including a nozzleopening therein, a duct carrying a 'fuel stream from said fuel bowl tosaid nozzle for injecting fuel into said mixture conduit, a meteringorifice in said fuel duct adapted to regulate the flow rate of said fuelstream, an air motor associated with said carburetor and having a firstpassage means connected to a source of varying vacuum in said engine,said air motor having a displaceable diaphragm at one wall thereofmoveable between inner and outer positions in response to variations insaid engine vacuum, said metering rod having opposed ends, one of saidends being disposed in said metering orifice, the other rod end engagingsaid diaphragm to reciprocate said rod between said inner and outerpositions in said orifice in response to a vacuum change in said airmotor, the improvement therein of; means forming a second passage incommunication with said air motor and having a port opening into saidmixture conduit, said throttle plate being moveable in said mixtureconduit between open and closed positions to regulate the speed of saidengine, and said throttle when positioned in the closed position in themixture conduit providing a sufificient passage for air fuel mixture tomaintain an engine. at idle speed and said throttle plate when in saidclosed position having an edge disposed immediately below said portopening into said mixture conduit, to prevent air flow through thelatter, and when said throttle plate is displaced slightly from saidclosed position, said port will be positioned upstream of said throttleplate edge to permit a metered flow of air through said second passageand into said first passage, whereby the degree of vacuum imposed onsaid diaphragm for urging said metering rod into the inner position isinstantaneously lessened thus permitting the air motor toinstantaneously actuate the metering rod a predetermined distance towardthe outer position to instantaneously form a greater fuel passage withthe metering orifice to provide an increased fuel flow to said mixtureconduit.

2. In a carburetor as defined in claim 1 wherein said first passagemeans communicates said air motor with the intake manifold of saidengine.

3. In a carburetor as defined in claim 2 wherein said first passagemeans includes a constricted'portion defining a limited opening forpassage of air therethrough.

4. In a carburetor as defined in claim 1 wherein said means forming afirst passage includes a channel formed in the wall of said carburetorbody and having a constriction therein to limit air flow therethrough.

5. In a carburetor as defined in claim 1 wherein, when said throttleplate is in the closed position, said edge of said throttle plate willbe positioned contiguous with the lower edge of said port opening intosaid mixture conduit.

6. In a carburetor as defined in claim 1 wherein said air motor includesbiasing means normally urging said diaphragm outwardly from the airmotor.

References Cited by the Examiner UNITED STATES PATENTS 2,404,645 7/ 1946Mallory 261-69 X 3,189,333 6/1965 Kalert et al. 26 l--69 3,222,039 12/1965 Newman et a1 26169 FOREIGN PATENTS 718,381 11/ 1954 Great Britain.

FRANK W. LUTTER, Primary Evaminer. RONALD R. WEAVER, Examiner.

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING AN INTAKEMANIFOLD INCLUDING; A BODY, A MIXTURE CONDUIT FORMED IN THE BODY, ATHROTTLE VALVE INCLUDING A THROTTLE PLATE CARRIED ON A THROTTLE SHAFT,THE LATTER BEING JOURNALLED IN THE MIXTURE CONDUIT AND BEING OPERABLE TOREGULATE THE PASSAGE OF AIR AND FUEL MIXTURE THERETHROUGH, A FUEL BOWLFORMED IN SAID BODY HOLDING A SUPPLY OF FUEL, A VENTURI IN SAID BODYINCLUDING A NOZZLEL OPENING THEREIN, A DUCT CARRYING A FUEL STREAM FROMSAID FUEL BOWL TO SAID NOZZLE FOR INJECTING FUEL INTO SAID MIXTURECONDUIT, A METERING ORIFICE IN SAID FUEL DUCT ADAPTED TO REGULATE THEFLOW RATE OF SAID FUEL STREAM, AN AIR MOTOR ASSOCIATED WITH SAIDCARBURETOR AND HAVING A FIRST PASSAGE MEANS CONNECTED TO A SOURCE OFVARYING VACUUM IN SAID ENGINE, SAID AIR MOTOR HAVING A DISPLACEABLEDIAPHRAGM AT ONE WALL THEREOF MOVEABLE BETWEEN INNER AND OUTER POSITIONSIN RESPONSE TO VARIATIONS IN SAID ENGINE VACUUM, SAID METERING RODHAVING OPPOSED ENDS, ONE OF SAID ENDS BEING DISPOSED IN SAID METERINGORIFICE, THE OTHER ROD END ENGAGING SAID DIAPHRAGM TO RECIPROCATE SAIDROD BETWEEN SAID INNER AND OUTER POSITIONS IN SAID ORIFICE IN RESPONSETO A VACUUM CHANGE IN SAID AIR MOTOR, THE IMPROVEMENT THEREIN OF; MEANSFORMING A SECOND PASSAGE IN COMMUNICATION WITH SAID AIR MOTOR AND HAVINGA PORT OPENING INTO SAID MIXTURE CONDUIT, SAID THROTTLE PLATE BEINGMOVEABLE IN SAID MIXTURE CONDUIT BETWEEN OPEN AND CLOSED POSITIONS TOREGULATE THE SPEED OF SAID ENGINE, AND SAID THROTTLE WHEN POSITIONED INTHE CLOSED POSITION IN THE MIXTURE CONDUIT PROVIDING A SUFFICIENTPASSAGE FOR AIR FUEL MIXTURE TO MAINTAIN AN ENGINE AT IDLE SPEED ANDSAID THROTTLE PLATE WHEN IN SAID CLOSED POSITION HAVING AN EDGE DISPOSEDIMMEDIATELY BELOW SAID PORT OPENING INTO SAID MIXTURE CONDUIT, TOPREVENT AIR FLOW THROUGH THE LATTER, AND WHEN SAID THROTTLE PLATE ISDISPLACED SLIGHTLY FROM SAID CLOSED POSITION, SAID PORT WILL BEPOSITIONED UPSTREAM OF SAID THROTTLE PLATE EDGE TO PERMIT A METERED FLOWOF AIR THROUGH SAID SECOND PASSAGE AND INTO SAID FIRST PASSAGE, WHEREBYTHE DEGREE OF VACUUM IMPOSED ON SAID DIAPHRAGM FOR URGING SAID METERINGROD INTO THE INNER POSITION IS INSTANTANEOUSLY LESSENED THUS PERMITTINGTHE AIR MOTOR TO INSTANTANEOUSLY ACTUATE THE METERING ROD APREDETERMINED DISTANCE TOWARD THE OUTER POSITION TO INSTANTANEOUSLY FORMA GREATER FUEL PASSAGE WITH THE METERING ORIFICE TO PROVIDE AN INCREASEDFUEL FLOW TO SAID MIXTURE CONDUIT.